Production of succinic and maleic acids from butyrolactone



Sept. 25, 1945. R. M. ISHAM PRODUCTION OF SUCCINIC AND MALEIC ACIDS FROMBUTYROLACTONE Filed June 12, 1941 q 05, 92.00am A v 31110144 041Rcljeri' M ZS/ZCUIZ/ Patented Sept. 25, 1945 PRODUCTION OF SUCCINIC ANDMALEIO ACIDS FROM BUTYROLACTONE Robert M. Isham, Ohmulgee, Okla,assignor to Danclger Oil & Refineries, Inc., Fort Worth, Tex., acorporation of Texas Application June 12, 1941, Serial No. 397,810

12 Claims. (01. zoo-311) This invention relates to the production ofsuccinic and maleic acids from butyrolactone.

In recent years, in the synthetic resin industry, the development of thealkyd type resins has been outstanding. These resins, which are thereaction products of polyhydric alcohols and dibasic acids, have foundwide use and acceptance. In this type or material the anhydrides of thealiphatic dibasic acids such as succinic and maleic anhydrides are ofdistinct importance being valuable not only for the production of thealkyd type resins but also serving very effectively as modifiers for thephenolic and urea resins. The demand for such acids has thus greatlyincreased.

As has been explained in prior applications Serial Nos. 326,112 and326,113, filed March 26, 1941, and No. 330,198, filed April 17, 1940, itis now possible to obtain butyrolactone in substantial quantities fromcheap source materials, namely pyroligneous acid residues.

The present invention deals with the production of succinic and maleicacids from such readily available source material by an efllcient andeconomical method, namely by the catalytic vapor phase exidation ofbutyrolactone.

It is known in the art that butyrolactone can be oxidized to succinicacid. The methods pro posed heretofore contemplated the oxidation of thelactone by chemical oxidizing agents, such as nitric acid, chromic acid,permanganates and the like. Such methods were attended with certaindisadvantages important among which was the difilculty ofrecoveringsuccinic acid from the reaction mixtures.

As a result of extensive experimentation in this field it has been foundthat the described conversion may be simply and eifectively accomplishedby direct oxidation methods. As described in copending applicationSerial No. 397,809, filed June 12, 1941, this conversion may be effectedby anodically oxidizing butyrolactone to succinic acid in a simpleelectrolytic cell. The

'present method deals with another method of conversion, similarlydirect and effective, namely, the vapor phase oxidation of butyrolactoneto produce succinic and maleic acids.

The present invention, briefly considered, comprehends the catalyticvapor phase oxidation of butyrolactone. The conversions involved proceedgenerally according to the following equations:

tively simple there are certain difliculties in volved. The oxidationreactions are accompanied by certain undesirable side reactions in whichthe four membered carbon chain is ruptured and products, such as carbondioxide, acetaldehyde and acetic acid are formed. These decrease theyield of the desired products and complicate their recovery. It has beendetermined that these side reactions may be minimized and a concomitantincrease in yield of the dibasic acids insured by carefully'controllingthe relative proportion of oxygen employed in the reaction andcontrolling the temperature in definite correlation with the catalystemployed to within definite optimum ranges.

It has been ascertained equal, and with a particular catalyst theundesirable side reactions may be reduced by op erating at relativelylow temperatures, that is to say, it has been learned that the primaryreaction (lactone to dibasic acid) proceeds preferentially or more orless selectively at lower temperatures.

The particular temperature or temperature range which is most effectivewill in turn vary somewhat depending upon the particular catalyst whichis utilized. For example, it. has been determinedthat when utilizingvanadium pentoxide and air as the oxygen supplying medium in the properratio of the reactants the'reaction proceeds best at between about 220C. and 250 C.

that, other things being It is clearly to be understood that this is anop timum and not the limited operable range of temperature; below 220 C.reaction does take place but the rate is considerably lowered;conversely above 250 0. reaction proceeds but with an inordinateformation of the undesired side reaction products. It has been furtherfound that with this particular catalyst oxidation of butyrolactone tothe dibasic acids proceeds at temperatures up to 370 C. but at thiselevated range the yield of the dibasic acids is quite low.

As noted above, the temperature range which is chosen for a particularoperation should be correlated carefully with the particular catalystemployed. Thus if copper oxide is Used in lieu of vanadium pentoxide,for the best results the operating temperatures should be about 50 C.above those employed when using vanadium pentoxide.

It has also been ascertained that an important determinant inestablishing an effective operation and securing a satisfactory yield isthe proportioning of the oxygen to the butyrolactone in the reactionsystem. It has been established that a large excess of oxygen favors theundesired side reactions. Although reasonably good results have beenobtained with a molecular ratio of oxygen to butyrolactone of 6 to 1 itis found in practice that best results are secured by establishing andmaintaining this ratio at about 2 to 1.

The catalyst employed in the process may be utilized in any desired formbut it is preferred to employ it supported on granular, inert material,

such as pumice or granular aluminum. The aluminum is especiallypreferred because, by reason tenuated form so as to insure optimumcontact with the reacting vapors. Very satisfactory results have beenobtained by using as the catalytic mass 10% by weight of vanadiumpentoxide supported on granular aluminum.

The operation of the process will be more readily appreciated and itsefiicacy evaluated by a consideration of a preferred mode of operation.In order more fully to describe the invention a typical, illustrativeapparatus, in which it is carrled out, is shown diagrammatically in thesingle figure of the accompanying drawing.

As shown in the drawingoxygen or an oxygencontaining gas, such as air,is fed through the coil I, positioned in furnace 2. in order to preheatsuch air to the desired temperature. The air thus preincreased heated isfed continuously to the lower portion of the bubble column 3.Simultaneously a charge of butyrolactone is fed to the column throu hthe line 4. 'In these circumstances the preheated air countercurrentlycontacts the downwardly flowing butyrolactone and the butyrolactone isvaporized and homogeneously mixed with the air. As noted previously. itis highly desirable to maintain a proper ratio or proportion of oxygento butyrolactone. This may effectively be done by controlling thetemperature of the preheated air admitted to column 3. In a typicaloperation, when air is utilized as the oxygen-supply medium, a vaporairmixture containing approximately 2 mols of oxygen to which 1 mol ofbutyrolactone may be produced by heating the air in coil l to atemperature of about 130 C.

The column 3, as will be appreciated, consti-- tutes a simple means forestablishing a properly proportioned, potentially reactive vapor phasemixture of butyrolactone and oxygen and the heating coil not onlysubserves the function of preheating one of the reactants, i. e. oxygen,but also, by reason of the temperature control it serves, so to speak,as a metering device establishing the optimum proportions of thereactants. The vapor-gas mixture is withdrawn from the top of the column3 and unvaporized butyrolactone collecting in the base of the tower maybe returned by line 5 and pump 5' back to the charging line 4.

The proper proportionsof the reactants having been established asdescribed, the mixture is then heated to reaction temperatures and thencontacted with the desired catalyst to insure oxidation. As shown, thisis done by passing the gasvapor mixture from the top of the towerthroimh the coil 6 which is located in the furnace I. It has been foundthat salutary results are insured by constructing the coil 6 of aluminumsince this has no catalytic effect on the reactants and thus tends toprevent or inhibit premature oxidation. In the coil 6 the mixture israised to that temperature which is most suitable for reaction in viewof the particular catalyst which is employed.

The properly proportioned heated mixture is then contacted with acatalyst. As shown, this is done by passing the mixture downwardlythrough the tubes 9 which are mounted within the chamber or container 8.The tubes are packed with the particular catalyst which is to be used,

i. e. vanadium pentoxide, copper oxide and the like, preferablysupported on granular material as previously described. The catalyst maybe retained in the tubes by a suitable means, such as the foraminousmembers or screens 9' attached to the lower ends of the tubes. Thecatalytic chamber 8 may be maintained at the desired temperature by anysuitable means, as for example by heating the tubes by indirect contactwith a liquid heating medium. This medium which, for example, may be ahydrocarbon oil, is admitted through line H and discharged through lineH). While it is notshown, lines II and I2 may be connected in a closedcircuit which includes a pump, together with heating and cooling meanswhereby the proper temperature may be maintained in unit 8 and theexcessive heat of reaction removed.

In the passage through the catalytic chamber reaction proceeds accordingto Equations 1 and 2 given above to produce succinic and maleicanhydrides. The reaction mixture passes outwardly of the chamber throughthe line I 2 and contacts the scrubbing medium, such as water.introduced into column I 3 through line H and scrubs the upwardlyflowing reaction mixture. The water flowing through line I! anddownwardly over the plates of the column dissolves any unalteredbutyrolactone and converts the succinic and maleic anhydrides to therespective acids and dissolves these acids. The upper portion of thecolumn is pro- Vided with the condenser 15, which may be of the "tubulartype which-is cooled by a suitable medium, such as water,.enteringthrough line l6 and discharging through line l1. In this condensersection any, water evaporated by the hot gases is butyrolactone as wellas side reaction products,

collects in'the base of the tower and is withdrawn through line I8. Thissolution may be treated tween about 220 C. and 250 by suitable methodsto separate the individual components, as for example by distillationand/or crystallization and the like.

An operation conducted according to the foregoing description isparticularly effective. In a typical operation employing an apparatus ofthe type described, butyrolactone was evaporated into air in the column3 at a temperature of 130 C. The catalytic unit was maintained at atemperature of 235 C. and the reaction mixture was passed through theapparatus so that the contact time in the catalytic unit 8 wasapproximately seconds. On analysis of the recovered products it wasfound that 95% of the butyrolactone was oxidized and that 77% of thebutyrolactone was converted to succinic and maleic acids in the ratio of6 to 4. In this operation the catalyst employed consisted of vanadiumpentoxide supported on granular aluminum in the proportion of 1 part byweight of the catalyst to 9 parts of aluminum.

It will be appreciated that the present method is as effective as it issimple. It will be observed, too, that the yields achieved with thisprocess are very high and compare most favorably with comparableoperations in the art. For example, in the past maleic acid has beenproduced by the oxidation of benzene at temperatures of the order of 400C. In such operations a recovery of 60% is considered very good. In thepresent process, as indicated, a yield of over 75% of the desiredproducts is easy to achieve.

The products produced by the present process, after separation orfractionation, may be used directly in the arts, as for example in theproduction of plastics. If desired these products may be further treatedas by esterification to produce valuable solvents. Again, if desired thefractlonated maleic acid may be hydrogenated to succinic acid orhydrated to malic acid for use in food products. The invention thuscomprehends the concept of producing succinic or maleic acid or anydesired derivatives thereof from cheap source materials by the simple,direct oxidation method outlined.

I claim:

1. That method of producing succinic acid which comprises oxidizingbutyrolactone, in vapor phase and at a temperature of between about 220C. and 250 C., and in contact with a catalytic material chosen from thegroup consisting of vanadium pentoxide and copper oxide which promotesthe oxidation.

2. That method of producing maleic acid which comprises subjectingbutyrolactone to vapor phase oxidation at elevated temperatures bewith acatalyst chosen from the group consisting of vanadium pentoxide andcopper oxide.

3. A method of treating butyrolactone to produce valuable productstherefrom which comprises, mixing butyrolactone, in vapor phase, with anoxygen-containing gas and in the proportions of about 2 mols of oxygento 1 mol of butyrolactone, contacting the mixture, at reactiontemperatures between about 220 C. and 250 C., with a catalyst whichpromotes the oxidation of butyrolactone and recovering a reactionproduct containing appreciable percentages of succinic and maleic acids.

4. A method of treating butyrolactone to produce valuable productstherefrom which comprises, mixing butyrolactone, in vapor phase, with anoxygen-containing gas and in the proto 1 mol of portions of about 2 molsof oxygen C. and in contactbutyrolactone, contacting the mixture, atreaction temperatures between about 220 C. and 250 C., with a catalystchosen from the, group con sisting of vanadium pentoxide and copperoxide which promotes the oxidation of butyrolactone, contacting theproducts of oxidation with water and recovering a reaction productcontaining appreciable percentages of succinic and maleic acids.

5. A method of treating butyrolactone to recover valuable productstherefrom which comprises, preheating an oxygen-containing gas,utilizing such preheated gas to contact and vaporize butyrolactone toproduce a vapor phase mixture containing about 2 mols of oxygen to about1 mol of butyrolactone, contacting the resulting gas-vapor mixture atelevated temperatures between about 220 C. and 250 C. with a catalystchosen from the group consisting of vanadium pentoxide and copper oxidewhich promotes the formation of succinic and maleic anlrvdrides.

6. A method of treating butyrolactone to recover valuable productstherefrom which comprises, preheating an oxygen-containing gas.utilizing such preheated gas to contact and vaporize butyrolactone toproduce a vapor phase mixture containing about 2 mols of oxygen to about1 mol of butyrolactone, contacting the resulting gas-vapor mixture atelevated temperatures between about 220 C. and 250 C. with a catalystchosen from the group consisting of vanadium pentoxide and copper oxidewhich promotes the formation of succinic and maleic anhydrides,contacting the reaction products with water to recover succinic andmaleic acids.

7. A method of treating butyrolactone to recover valuable productstherefrom which comprises, preheating an oxygen-containing gas,utilizing such preheated gas to contact and vaporize butyrolactone toproduce a vapor phase mixture containing about 2 mols of oxygen to about1 mol of butyrolactone. contacting the resulting gas-vapor mixture atelevated temperatures between about 220 C. and 250 C. with a catalystwhich promotes the formation of succinic and maleic anhydrides,contacting the reaction products with water to recover succinic andmaleic acids and separating and recovering such succinic and maleicacids.

8. In the vapor-phase oxidation of butyrolactone to succinic and maleicanhydrides, that improvement which comprises, vaporizing'butyrolactoneby contact with a heated oxygen-containing gas to produce a vapor phasemixture containing approximately 2 mols of oxygen to 1 mol ofbutyrolactone and oxidizing such mixture at a temperature of betweenabout 220 and 350 C. in the presence of a catalyst chosen from the groupconsisting of vanadium pentoxide and copper oxide.

9. In the vapor phase oxidation of butyrolactone to produce succinic andmaleic anhydrides that improvement which comprises, preheating air,passing the air countercurrently to a stream of butyrolactone to therebyvaporize the butyrolactone and intimately mix such vapors with the airto produce a vapor phase mixture containing approximately 2 mols ofoxygen to 1 mol of butyrolactone, heating the vapor-gas mixture totemperatures of between about 220 C. and 250 C. which favor theoxidation of butyrolactone to succinic and maleic anhydrides andcontacting the heated mixture with a catalyst chosen from the groupconsisting of vanadium pentoxide and copper oxide to produce succinicand maleic anhydrides. V

10. In the vapor phase oxidation of butyroiactone that improvement whichcomprises preheating a mixture of butyrolactone vapors and air to atemperature between about 220 C. and 250' C. in a container composed ofaluminum and then contacting the heated mixture with a catalyst whichpromotes the oxidation of the butyrolactone to succinic and maleicanhydrides.

11. A method of producing succinic and maleic anhydrides which comprisespreheating air to a. temperature of the order of 130 0., contacting suchpreheated air with a solution of butyrolactone to vaporize thebutyrolactone to establish 15 a vapor phase mixture in the approximateratio of 2 mols of oxygen to 1 moi of butyrolactone, heating the mixturein a separate heating zone to a temperature between approximately 200 C.and 375 C., passing the heated mixture in contact with a catalyticmaterial which promotes the oxidation 01' butyrolactone and withdrawingthe r reaction products containing succinic and maleic anhydrides.

12. A process in accordance with claim 11 in which the reaction productsare scrubbed with water to recover an aqueous solution containingsuccinic and maleic acids.

ROBERT M. ISI-IAM.

